DESCRIPTION: The overall goal of the laboratory's research is the behavioral, physiological, and anatomical correlates of echolocation and hearing in the mustached bat. This proposal focuses on two main themes: control of the cochlea by OC efferents and 3D imaging of the inner ear. There are five specific aims: 1. Monitor MOC activity and induced changes in cochlear mechanics during echolocation. This includes the demonstration of phasic activity in relation to the emission of pulses and perception of echoes and tonic activity in relation to the total acoustic input over time. 2. Demonstrate links between MOC activity, acoustic perception, echolocation behavior (DS compensation) and neural correlates of echolocation (e.g. tuning curve sharpness). 3. Determine the acoustic stimulus parameters that cause the breakdown of MOC induced suppression of cochlear damping and demonstrate that this breakdown is due to the interaction, w/in the cochlea of ACh and GABA, the two transmitters known to mediate efferent activity. 4. Establish the peripheral course, distribution, and arrangement of LOC fibers and terminals in different functional areas of the cochlea (e.g. 60 - 90 kHz foveal regions and more broadly-tuned segments). 5. Complete the collection of MRM images of the cochleae of bats and other mammals and explore the modeling (finite element analysis - FEA) of vibrational patterns, given the dimensions of the cochleae reconstructed from MRM.